Field
The present disclosure relates to a filtration assembly for the filtration of ultra-fine particles from liquids or gases.
Description of Related Art
Filtration is an important method that typically is used to separate solids from fluids (gases or liquids) for a variety of industries, from oil and gas processing to even food processing industries. In most industrial processes that rely on filtration, the replacement of filtration media is very frequent, leading to significant cost increase and the rise of issues of processing or recovery of the solid wastes of used filtration media.
The filtration media currently available for industrial application are diverse. Popular types of media are meshes or other type of intertextures or assembly of fibered materials, cemented metals, and membranes. These filtration media have torturous pores along the filtration direction, namely the fluid passing paths. During the filtration operation, these tortuous pores are easily blocked by embedding solid particles and these embedding particles are hard to be removed by any methods, for example, back flushing or back-washing, leading to rapid defunctionalization of the media.
For some critical applications at elevated temperatures and higher pressures, for example, in solid removal from waxy fluids, the sintered rigid metal meshes or sintered metal powder media are often used equipped with back flushing. Due to the blockage of the pores and/or mechanical damage (especially for rigid mesh type media), the life span of the filtration media is rather short, causing frequent unit shut down for replacement of filtration media.
There have been cases requiring in-situ filtration systems in chemical reactors, separation towers, and/or in an integrated machinery unit (e.g., in oil and gas industries). In cases like these, the filtration schemes commonly used are of tubular type of filters made of metal mesh media for easing regeneration by back washing (flushing). One common issue is the frequent replacement of filtration elements due to blockage or damage of filtration media. The filter tends to fail because of solids embedding in the pores of the filtration media. Because long term running is required in situations like these, shutdown of the systems (and, in some cases, a whole plant) for changing of the filters, or for back washing, is inconvenient and may be costly. Processes, such as the Fischer-Tropsch process, which require separation of solids from a suspension containing liquids, solids, and gases, require filtration units that must be back-flushed periodically, which can result in significant losses due to process interruptions. Filtration systems disclosed for such process are described in, for example, U.S. Pat. Nos. 5,599,849; 5,844,006; 7,378,452; 7,488,760; 8,022,109; and 8,778,193, the disclosures of each of which are incorporated by reference herein in their entireties.
Further, some filter systems use a filter web or filter fabric around an outer perimeter as a main filtering medium, or such that the filtration process takes place on the filter web or filter fabric. U.S. Pat. No. 4,473,472 and U.S. Pat. No. 6,041,944 provide examples utilizing a surrounding web or fabric. Such designs, however, are still subject to easy blockage and frequent replacement. Moreover, the surrounding filter web or filter fabric is typically placed around filter elements (or a bundle), and thus the surface area of the filter elements is not utilized effectively.
By changing the filter media and design of the structure, blockage of filtration pores may be avoided while maintaining or improving mechanical strength of the filter element.